The present invention relates to a system and method for detecting and locating an acoustic event. More particularly, but not by way of limitation, the present invention provides a highly portable gunshot detection system.
Gunfire and sniper detection systems are generally known in the art. Such systems can be broadly grouped into three categories: systems which pinpoint the precise location of the source of gunfire; azimuthal sensors which provide an indication of the radial direction to the source of gunfire; and proximity sensors which merely provide an indication that nearby gunfire was detected. While such systems have been demonstrated to perform in both law enforcement and military applications, the entire field is presently an emerging technology.
In many large cities, gun-related violence has become a plague of epidemic proportions. Urban gunfire, whether crime-related or celebratory in nature, results in thousands of deaths per year in the United States alone. Gunfire location systems, such as those installed in the Redwood City, Calif., Glendale, Ariz., Willowbrook, Calif., City of Industry, Calif., and Charleston, S.C. areas, have proven to be effective in reducing law enforcement response time to detected gunfire, apprehending criminals, collecting evidence, and reducing the occurrence of celebratory gunfire. One such system is described in U.S. Pat. No. 5,973,998, issued to Showen, et al., which is incorporated herein by reference.
Showen, et al. discloses a system wherein sensors are placed at a density of roughly six to ten sensors per square mile. Audio information is sent to a computer at a central location and processed to: detect a gunshot; determine a time of arrival for the gunshot at each sensor; and calculate a location of the shooter from the differences in the times of arrival at three or more sensors. Showen, et al. takes advantage of the long propagation distance of gunfire to place sensors in a relatively sparse array so that only a few of the sensors can detect the gunfire. This permits the processor to ignore impulsive events which only reach one sensor—a concept called “spatial filtering.” This concept of spatial filtering radically reduces the sensor density compared to predecessor systems, which require as many as 80 sensors per square mile.
Another gunshot location system is described in co-pending U.S. patent application Ser. No. 10/248,511 by Patterson, et al., filed Jan. 24, 2003, which is incorporated herein by reference. Patterson, et al., discloses a system wherein audio information is processed within each sensor to detect a gunshot and determine a time of arrival at the sensor. Time of arrival information, as determined from a synchronized clock, is then transmitted wirelessly by each sensor to a computer at a centralized location where a location of the shooter is calculated in the same manner as in the Showen, et al. system.
As yet, azimuthal systems have not been as widely accepted as, for example, the Showen, et al. system. Azimuthal sensors typically employ one or more closely-spaced sensors, where each sensor includes several microphones arranged in a small geometric array. A radial direction can be determined by measuring the differences in arrival times at the various microphones at a particular sensor. Presently such systems suffer from somewhat limited accuracy in the determination of the radial angle, which in turn, translates into significant errors in the positional accuracy when a location is found by finding the intersection of two or more radial lines, from corresponding sensors, directed toward the shooter. Since errors in the radial angle result in ever increasing positional error as the distance from the sensor to the source increases, the reported position will be especially suspect toward the outer limits of the sensors' range.
A concern unaddressed by the present art is a portable system for gunshot detection and location. In particular, an array of portable sensors in combination with individual display devices and a portable server. Patterson, et al. discloses a portable sensor having a belt clip but fails to disclose a portable system.
For example, in a military environment, merely detecting a gunshot and providing a source location at a central location is ineffective. A soldier must be provided the source location in a meaningful manner and in a meaningful time frame to return fire and/or take cover or the system has failed to attain its goal.
Similar issues arise in law enforcement applications during tactical operations such as during sniper incidents, hostage situations, and the like. Rapid deployment is only partially addressed by a wireless sensor. Infrastructure for communication with a server and providing meaningful information to the people who need the information requires more than a mere portable sensor.
Some existing azimuthal sensors are suitable for rapid placement but are not actually portable in the sense that individual soldiers or officers cannot wear or carry the sensors operationally and there is no provision for instantaneous display to the individual solder that is actually being fired upon.
It is thus an object of the present invention to provide a highly portable system for the detection and location of gunfire wherein all components of the system are portable and the system provides near immediate information directly to individuals who are directly in the line of fire.